Universal starting bar



1969 R. w. CRUGER ETAL 3,429,366

UNIVERSAL STARTING BAR Filed Nov. 22, 1966 INVENTORS ROBERT W. CRUGER BY ANATOL MICH ELSON 7M 5 United States Patent F 6 Claims ABSTRACT OF THE DISCLOSURE The disclosure pertains to a roller apron and starting bar designed for use with a continuous casting mold. The roller apron may be either curved or straight and comprises inner and outer sections, at least one of which is movable relative to the other to accommodate different sizes of ingots to be cast. The starting bar comprises a head providing a temporary bottom for the mold to which the ingot is initially attached and a driver section detachably connected to the starting bar head for inserting and withdrawing it along the roller apron composed of a series of links having a thickness not greater than the minimum thickness of ingot, the driver section being guided entirely on one of the roller apron sections independently of the other section whereby only the starting bar head requires replacement when a different ingot size is cast.

The invention pertains to the art of continuous casting in which a vertical, water-cooled, flow-through mold, either curved or straight, is provided with a temporary bottom in the form of a starting bar head at the start of a casting cycle. Molten metal is poured into the mold which solidifies and attaches to the head. Pouring continues as the head is withdrawn slowly from the mold pulling the ingot with it into the roller apron.

Heretofore starting bars, even of the flexible type suitable for curved withdrawal, are used only for one thickness of ingot. Inasmuch as the roller apron defines the ingot withdrawal and cooling path, it must have a gap equal to the ingot thickness and since the starting bar is inserted through the roller apron to begin with, its thickness must likewise equal the ingot thickness. If the starting bar were made thinner than the ingot it could not pass through the roller apron because the flexible sections or links would be free to jackknife against the inner and outer roller apron sections and would become wedged between the rolls. This means that a continuous casting machine must be provided with as many starting bars as there are ingot sizes to be cast in the machine. For example, a machine intended to cast five sizes of ingots has to have five different starting bars. These bars are quite heavy, bulky and expensive. For instance, the weight of one bar for a slab with a cross sectional area of 12 inches by 80 inches is approximately 180,000 pounds and its length is about 80 feet.

The initial capital investment of a continuous casting machine is quite high by itself without adding an additional amount for the complement of starting bars required. Moreover, storage space for a number of starting bars in the casting plant and the necessity of auxiliary handling equipment to change the bars coupled with the loss of time and labor involved in replacement of starting bars and readjustment of the casting machine with each new ingot size are major shortcomings of conventional practice.

These difficulties and others are overcome with the present invention which provides, in combination, a roller apron and starting bar in which separate guidance of the starting bar and the ingot make possible the use of one 3,429,366 Patented Feb. 25, 1969 starting bar for all sizes of ingots to be cast, i.e., a universal starting bar.

In accordance with the invention, a continuous casting machine capable of casting various sizes of ingots includes a mold and a roller apron defining an adjustable ingot withdrawal and cooling path extending from the mold a substantial distance. A starting bar is composed of a head insertable into the mold to provide a temporary bottom upon which the ingot may solidify and attach and a driver section detachably connected to the head having a thickness not greater than the smallest size of ingot to be cast. A track generally following the withdrawal and cooling path guides the starting bar to and from the mold, but independently of the path which guides the ingot whereby the starting bar head may be replaced by one of a different size without replacing the driver section.

Further in accordance with the invention, the track includes parallel rails mounted on opposite sides of one of the roller apron sections and the driver section is guided by the rails positioned on the outer extremities thereof. A tapered link between the driver section and head provides the dimensional transition necessary to smoothly pass the starting bar through withdrawal rolls.

Further in accordance with the invention, the roller apron defines a curved withdrawal and cooling path having an inner convex roller apron section facing an outer concave roller apron section, the inner section being movable relative to the outer section to vary the withdrawal and cooling path spacing therebetween and the rails including a plurality of concavo-convex rail sections mounted on opposite sides of the inner roller apron section so as to maintain a constant guidance gap for the driver section regardless of the adjustment of roller apron withdrawal and cooling path spacing.

A principal object of the invention is to provide one starting bar for all sizes of ingots regardless of the size to be cast in a particular machine thereby reducing the cost of the machine, eliminating the need for storage space for bars not in use, eliminating the need for handling equipment for the exchange of bars and providing a savings of time and labor otherwise needed for the exchange of bars.

As a further object of the invention, the roller apron and starting bar coact in such a manner that separate guidance for the ingot and for the starting bar is provided thus eliminating the need for different sizes of bars.

A further object of the invention is to provide a starting bar composed of a series of links, the leading one of which provides a gradual dimensional transition between the thickness of the driver section and the starting bar head to properly negotiate withdrawal rolls.

These and other objects will become apparent by referring to the following description and drawings wherein:

FIGURE 1 is a side elevational view of a curved continuous casting installation utilizing a starting bar and roller apron as provided in the invention;

FIGURE 2 is a cross sectional view through the starting bar and roller apron of FIGURE 1 taken along line 22; and

FIGURE 3 is a fragmentary side view of the entry end of the roller apron showing the starting bar head being inserted toward the mold.

Referring now to the drawings wherein the figures are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGURE 1 depicts a curved casting installation 10 composed of a curved, water-cooled, flow-through mold 12 into which molten metal 13 is poured from a container or ladle 14 positioned above. Below the mold, a roller apron 16 supports a starting bar 18 composed of a head 20 and a driver section 22. It will be understood by those familiar with continuous casting machines that as the metal 13 is poured into the mold 12 it commences to solidify on the starting bar head which provides a temporary bottom for the mold. Pouring continues as the head 20 is withdrawn slowly from the mold pulling with it an ingot having a vertical cross sectional Shape corresponding to that of the mold 12, in this case, having a center of curvature at a radius R. The head 2!) guides the ingot into the withdrawal and cooling path, 24 defined by the roller apron 16. While in the preferred embodiment, a curved mold is disclosed, it will be understood that the invention does not depend on this and that it is also applicable to a straight mold casting machine which may or may not employ bending and withdrawal rolls for changing the direction of the ingot from a vertical to a horizontal path.

In the preferred embodiment of the invention, the roller apron 16 includes inner and outer sections 26, 28, each composed of roller elements 29, having rolls 38, 38 which together define the concavo-convex withdrawal and cooling path 24. The roller elements 29 of the inner track ection 26 are mutually displaceable relative to their counterparts, roller elements 38 of the outer track section 28, in a radial direction so as to vary the width of the withdrawal and cooling path 24. Apron support and adjustment mechanism, not shown, is provided for supporting the roller elements 30 of the outer section 28 in fixed relationship to the movable roller elements 29 of the inner section 26.

The driver section 22 of the starting bar 18 is composed of a series of interconnected links 23 which may be either curved or straight, and is suffiicently long to reach from the mold 12 to a pair of pinch rolls 32 when the starting bar head 20 is inserted in the mold as shown in FIG- URE 1. In the preferred embodiment, the links 23 are shown curved with a radius R Each link is the same length which practically is limited to the distance D between a second pair of pinch rolls 35, 36. If straight, however, the links should have a length less than two pinches of rolls 38 of the roller apron 16. That is, if straight, the length of each link 23 should not exceed the distance between three successive rolls 38. Each link is connected to the adjacent link by a transverse pin 40 extending alterally beyond the maximum width of the withdrawal and cooling path 24, which in thep referred embodiment, is designed for slabs having a minimum and maximum width as may be seen by inspection in FIG- URE 2. Secondary cooling of the ingot slab is provided by spray jets 42 connected to water supply mains 43 and directing a spray of water generally between the support rolls 38, 38' of the roller apron.

The starting bar 18 is guided to and from the mold on parallel curved rails 48 supported on opposite sides of the inner roller apron section 26 generally following the curvature of the withdrawal and cooling path 24. Each rail 48 is composed of concave-convex rail sections 49 (FIG. 3) upon which run extensions 44, 46 of each pin 40. The rail sections 49 have a radius of curvature equal to the radius R plus /2 the diameter of the pin extensions 44, 46 so that the axis of rotation of pins 40 is along a curved path having the radius R. A gap 50 at the ends of adjacent rail sections 49 is sufiiciently small at the narrowest spacing of the roller apron sections to be easily negotiated by the pin extensions 44, 46.

In accordance with the invention, each link 23 is no thicker than the minimum thickness of ingot adapted to be cast in the machine 10. However, the starting bar head 20 obviously must have a cross sectional dimension equal to that of the mold since it acts as a temporary mold bottom. The invention contemplates therefore, that the starting bar head 20 be deachably connected to the first link 23 by means of a dimensional transition link 53 (FIG. 3) which is tapered on one side 54 from the minimum thickness of link 23 to the maximum thickness of the head 20. The opposite surface 55 of the link 53 is curved at the radius R the same as links 23. A disconnect coupling 56 for the dimensional transition link 53 and starting bar head 20 is provided which may be automatically triggered upon withdrawal to release the starting bar driver section 22 at the proper time. A quick disconnect coupling of the type which may be used is disclosed in US. patent application Ser. No. 549,232 filed May 11, 1966 entitled Starting Mechanism For Continuous Casting Machine assigned to the assignee of the present invention.

Thus the starting bar driver section 22 is composed of a series of links 23 each of which is supported on rails 48 at the lateral extremities thereof during insertion toward the mold, which support is entirely independent of the outer section 28. During withdrawal the links 23 are under tension and are supported entirely on rolls 38. The starting bar head 20, and of course the ingot, are guided independently by the rolls 38, 38' of both sections 26, 28 of the roller apron 16 during insertion and withdrawal. The dimensional transition link 53 is guided, due to its tapered shape, by the rails 48 and by the rolls 38, 38'.

Pinch rolls 32, 35, 36 should always smoothly contact the starting bar and ingot so that no sudden change between the vertical spacing of the top and bottom rolls takes place. To this end, each of the top rolls of the pinch roll stands 32, 35, 36 is under vertical pressure from individual hydraulic cylinders (not shown).

In operation, suppose it is intended to cast a slab 12" thick. Thus, links 23 of the starting bar have a maximum thickness of 5". At the start of a new casting cycle the starting bar 18 is in a special storage area to the right of pinch rolls 32. By means of other mechanisms (not shown) the starting bar 18 is fed into the pinch rolls 32 which are driven by 'motors and drive the starting bar into the roller apron 16. The quick disconnect coupling 56 first encounters an incline 60 (FIG. 3) which guides the driver section 22 of the starting bar into the entry of rails 48. As insertion continues, each link 23 will be successively lifted and guided into the rails 48. After the head 20 reaches the desired level in the mold 12, the pinch rolls 32 stop, halting the advance of the starting bar. During insertion the starting bar, being under the effect of its own weight only, is supported at the outer extremities by the rails 48.

After the molten metal has been poured and solidification progressed to the desired point, pinch rolls 32 start to rotate in the opposite direction to commence withdrawal of the starting bar and ingot. The pulling force provides tension on the bar and its links 23 press against the apron rolls 38 so that during withdrawal, the starting bar presses against and is supported mainly by the rolls 38 of the inner roller apron section 26 rather than by the rails 48 which merely serve as lateral guides.

When the tapered or dimensional transition link 53 comes to the pinch rolls 32, the top roll is pushed up as indicated by the dotted line positioning in FIGURE 1. Movement of the inclined surface 54 of the dimensional transition link 53 through the pinch rolls 32 results in the requirement for the application of additional withdrawal force by pinch rolls 35, 36 which force constitutes an increase over the normal withdrawal force depending upon the slope of the surface 54. The dimensional transition link 53 and starting bar head 20 precede the ingot through pinch rolls 35, 36 also causing a corresponding vertical displacement as they pass through.

Thus it may be seen that the invention primarily resides in separate guidance for the slab being cast and the starting bar, thus avoiding the disadvantages of the prior art occasioned by the use of as many different starting bars as there are thicknesses of ingot to be cast since both were guided by the same means.

Having now described a preferred embodiment of the invention, it will be appreciated by those skilled in the arts that various modifications may be made without departing from the invention as defined in the appended claims.

Having thus described our invention, we claim:

1. A starting bar for use in a continuous casting machine capable of casting various sized ingots including a mold and a roller apron defining an ingot withdrawal and cooling path extending from the mold a substantial distance, said starting bar comprising a head insertable in the mold to provide a temporary bottom upon which an ingot may solidfy and attach and a driver section detchably connected to the head having a thickness throughout its length not greater than the smallest sized ingot to be cast and track means adjacent to and generally following the withdrawal and cooling path for guiding said driver section independently of said starting bar head for guiding said driver section whereby the head may be replaced to accommodate a different ingot size without replacing the driver section.

2. A starting bar according to claim 1 wherein said roller apron is composed of opposed sections, one being movable relative to the other to define an adjustable withdrawal and cooling path, said traok means including parallel rails mounted on opposite sides of one of the roller apron sections and the driver section of said starting bar being guided and supported during insertion and withdrawal by said rails in cooperation with the roller apron section.

3. A starting bar according to claim 2 where the ingot to be cast is thicker than a predetermined minimum and said starting bar comprises linking means extending between the end of said driver section and said starting bar head providing a dimensional transition from the thickness of the head to that of the driver section.

4. A starting bar according to claim 2 for use with a casting machine having a curved roller apron defining a concave-convex withdrawal and cooling path, said driver section comprising a series of curved links joined end-to-end which have a concave-convex curvature approximately coinciding with said withdrawal and cooling path.

5. In a continuous casting machine capable of casting various sized ingots including a mold and a roller apron having opposed sections, one being movable relative to the other to define an adjustable ingot withdrawal and cooling path extending from the mold a substantial distance, the improvement comprising a starting bar including a head insertable in the mold to provide a temporary bottom upon which an ingot may solidify and attach and a driver section detachably connected to the head having a thickness not greater than the smallest ingot size to be cast and track means generally following the withdrawal and cooling path being supported on said movable roller apron section for guiding said driver section along said path independently of the starting bar head whereby the head may be replaced to accommodate a dilferent ingot size without replacing the driver section.

6. The improvement according to claim 5 wherein the roller apron is curved so as to define a concave-convex ingot withdrawal and cooling path and said track means includes parallel rails mounted on Opposite sides of the inner roller apron section on the outer extremity of said path whereby during insertion said driver section is guided and supported by said rails and during withdrawal is supported by said inner roller apron section.

References Cited UNITED STATES PATENTS 3,157,920 11/1964 Hess 164282X 3,351,124 11/1967 Hess 164274 FOREIGN PATENTS 1,376,998 9/1964 France.

I. SPENCER OVERHOLSER, Primary Examiner.

R. SPENCER ANNEAR, Assistant Examiner.

US. Cl. X.R. 193-35 

